CI: Install customized project

Avoid caching problem on Travis CI.

DO NOT MERGE

.travis.yml

@@ -24,6 +24,9 @@ matrix:
  - jdk: openjdk8
  - jdk: oraclejdk9
 
+install:
+ - make dcurl
+
 script:
  #run tests and integration tests
  # see https://stackoverflow.com/questions/34405047/how-do-you-merge-into-another-branch-using-travis-with-git-commands?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa